1. Field of the Invention
This invention relates generally to light therapy and more particularly to a therapy system utilizing light emitting diodes as a source of biostimulative noncoherent radiation.
2. Related History
Monochromatic light radiation at defined wave lengths has produced beneficial biostimulative effects and has been known to trigger specific biological functions, such as, phototaxis, photorepair, cell division and photoperiodics clocks. Stimulation occurred, however, with light radiation in controlled wave lengths and only in conjunction with controlled administration dosages. Application of broad band light radiation, overdosage, or inadequate dosage, did not provide the beneficial biostimulative effects.
While the exact mechanism by which the beneficial biostimulative effects have been achieved is not precisely known, several theories have been propounded. It has been suggested that monochromatic light radiation penetrated body tissue and was absorbed, reflected and scattered to excite molecules within damaged tissue to thereby accelerate repair.
A further theory suggested that different cells had different photoreceptors which responded to only particular wave lengths of light radiation. This theory supported the phenomenon that the application of only certain wave lengths of light radiation resulted in biostimulative effects. It was known that the application of too much light power did not produce biostimulative effects; this was possibly due to the destruction of the photoreceptors, while inadequate dosage resulted in the inability to trigger the photoreceptors.
Light therapy has utilized lasers with relatively low power and biostimulative treatment utilizing lasers has been referred to as "soft" laser therapy. In such applications, low level laser energy radiation has been successfully employed to stimulate wound healing and treat inflammatory conditions. In recent years, soft laser therapy has been successfully employed for the treatment of musculoskeletal disorders and skin ulcers. Both low level helium neon lasers and infra red lasers have been employed to generate radiation characterized by monochromacity and coherency. Soft radiation therapy utilizing helium neon lasers necessitated equipment which was relatively large and highly expensive and often required cooling systems. Such lasers were utilized to provide a continuous, relatively low power, e.g. in the range of 10 MW, beam of coherent radiation having sharply defined wave length which remained stable to within plus or minus 1 nm.
Infra red laser therapy utilized a laser system to generate a coherent beam of monochromatic sharply defined radiation in the infra red wave length band. The lasing medium utilized semiconductor diode. The output from the laser diode was a sharply diverted and conical and was difficult to couple efficiently to an optical system. Because of its coherency, it required diffraction limited collection, focusing and coupling optics which added significantly to the cost of the resulting system.
Laser diodes required higher operating currents than conventional light emitting diodes in order to maintain adequate population inversion by producing a high density of electron hole pairs. The resulting radiation was essentially monochromatic and coherent whereas the radiation of a conventional light emitting diode is noncoherent and encompasses a broader spectral bandwidth. Because of the relatively high current density through a laser diode, laser diodes could only be operated in a pulsed mode wherein the current sufficient to cause population inversion was passed through the diode as a pulse train comprising pulses of very short duration, e.g. in the order of nanoseconds. As a result, laser diode switching frequency was required to be extremely fast which necessitated complex and expensive power supplies.
Laser diodes did possess advantages over helium neon lasers for use in soft laser therapy, in part due to the fact that the physical system was less expensive than that of helium neon lasers. In addition, laser diode systems were relatively small in size as compared with helium neon lasers of equivalent power rating. Laser diodes to date have been available in the infra red frequency range.
It has been previously theorized that the properties of laser radiation which resulted in the beneficial biostimulative effects of soft laser therapy were the monochromacity and coherence of laser radiation.
There appeared to be a need for the beneficial effects of the continuous operating characteristics provided by helium neon lasers to be combined with the lower cost and higher output power of laser diode systems.
It occurred to applicants that if biostimulative light radiation effects of soft laser therapy were not predicated upon absolute monochromacity and coherency of the radiation and that radiation within a defined bandwidth range could result in biostimulation, conventional light emitting diodes could be utilized.